Natural fibers, such as cotton, wool and silk, and synthetic fibers such as nylon, acrylic and polyester, are used in the textile industry to produce apparel products such as knits and wovens, piled fabrics such as carpets, and consumer goods such as sheets and towels. These products undergo a number of processes to impart certain physical and aesthetic properties to satisfy consumer needs.
One of the major processes used in the production of textiles is that of coloration. In this process dyes are imparted to fibers to produce a myriad of visual effects on finished textile goods. Associated with the use of dyes are dye auxiliaries which aid in the dyeing process or in maintaining quality standards as defined by the end use. One of these standards is cold water bleed as measured by AATCC test method 107. Dyed textile goods display a tendency to transfer dye from fiber to fiber, yarn to yarn, and fabric to fabric when they are in aqueous contact with each other. The degree to which this transfer occurs depends on several factors such as fiber type, dye type and depth of shade. Thus one class of dye auxiliary is that which is employed to minimize or eliminate cold water bleed. These chemical auxiliaries are traditionally called "fixing agents". For example, nylon fixing agents are used to treat nylon textiles dyed with acid dyes while cotton fixing agents are used to treat cellulosic textiles dyed with fiber reactive, direct or vat dyed.
Some nylon carpet fibers are receptive to being dyed with acid dyes while other types of nylon fibers are receptive to being dyed with basic dyes which are referred to as cationic dyes. Basic, cationic dyeable nylon commonly contains SO.sub.3 H or COOH groups within their polymer structure in an amount sufficient to render the nylon fiber dyeable with a basic dye. Though cationic dyeable (CD) nylons offer good stain resistant properties, particularly to acid dye type stains, they have suffered from poor lightfastness, especially in light shades. This has greatly limited their commercial utilization.
The just described problem has recently been addressed and partially solved by dyeing CD nylon fibers with acid and premetallized acid dyes as disclosed in U.S. Pat. No. 5,085,667 of William G. Jenkins. Associated with this process, however, is increased cold water bleed to levels below acceptable standards in many shades of color.
Of additional importance in the textile industry is the colorfastness properties of nylon fibers since nylon fibers are of more general use than CD nylon fibers. Colorfastness, i.e., the resistance of a material to changing its color characteristics, is measured by colorfastness to water (commonly referred to as cold water bleed) and colorfastness to laundrying. Cold water bleed problems occur when nylon fibers such as polyamide fibers are dyed with acid or acid premetallized dyes. Generally, nylon fixing agents alone adequately reduce cold water bleed of most acid or premetallized acid dyed nylon. However, when darker shades of dye are used, especially blue shades, cold water bleed remains a problem even when a nylon fixing agent is employed. Further, nylon fibers dyed with acid or acid premetallized dyes have reduced colorfastness to laundrying in the darker shades.